Monophonic musical tone system with single keyed oscillator, pedal clavier, and percussion arrangement

ABSTRACT

In a monophonic musical instrument, a single oscillator is used to selectively produce any of several musical notes. Electronic switches are used to tune the oscillator, and a memory system is provided so that percussive sounds can be produced. Tuning, and signal gating functions are controlled by a single, one pole, one throw, keyswitch associated with each playing key of the instrument.

[Ill 3,562,395

United States Patent [56] References Cited UNITED STATES PATENTS [72] Inventor Richard H. Peterson 4 MM4 88008 o e mmw m TO 888 HHGM 3569 6666 9999 1111 ///l 4 2 1 11 8849 7102 93 9084 0000000 3333 Mum GooJF 0.. d N m .L n wm na AFP 1.11. 25 224 1:11

[54] MONOPHONIC MUSICAL TONE SYSTEM WITH Primary ExaminerW. E. Ray Attorney-Donald H. Sweet SINGLE KEYED OSCILLATOR, PEDAL CLAVIER, AND PERCUSSION ARRANGEMENT 3 Chums l Drawmg ABSTRACT: In a monophonic musical instrument, a single 84/1.0l, oscillator is used to selectively produce any of several musical notes. Electronic switches are used to tune the oscillator, and a memory system is provided so that percussive sounds can be produced. Tuning, and signal gating functions are controlled by a single, one pole, one throw, keyswitch associated with each playing key of the instrument.

9) m oP 1 7 h M 0 8 7 l M 9 J L, M W w 8 7 m m n" 6 1 m m2 M" 8 m m4 n "2 m mi N m9 M m m m m7 m m C3, m m m & m m e h F 1 l 1 0 5 5 l I AAA PATENTED FEB 9 I97! INVENTOR MONOPI'IONIC MUSICAL TONE SYSTEM WITH SINGLE KEYED OSCILLATOR, PEDAL CLAVIER, AND PERCUSSION ARRANGEMENT This invention relates to a monophonic tone generating system in which a single oscillator is selectively tunable to any one of a plurality of tone signal frequencies corresponding to notes of a musical scale. Monophonic instruments are those upon which it is possible to play but a single note at a time. Apparatus according to the invention can be effectively employed in connection with melody instruments of the keyboard type, or in connection with electrical instruments designed to simulate many of the sounds produced by conventional wind and string instruments.

A very important application for monophonic tone generators is in connection with the pedal clavier of electronic organs. It is usually necessary to play but a single pedal note at a time and for most applications it is an advantage not to be able to inadvertently play two or more notes which would likely result in a discord. ln the embodiment selected to illustrate the invention l have shown a complete pedal tone generating system for a 13 note pedal clavier such as might be employed with a small electronic organ.

One of the objects of the invention is to provide an independent pedal tone generating system capable of producing all of the pedal tones required in an instrument of this character, and wherein such tones are not synchronized or locked in tune with the tone generating equipment used for the manual playing keys of the organ. Because the tones generated by the pedal system can be adjusted to be slightly out of tune with the manual tone generator, a greatly enhanced chorus effect can be obtained.

Another object of the invention is to provide a monophonic tone generating system which is capable of producing tones having percussive intensity envelopes.

Still another object of the invention is to provide a monophonic tone generating system wherein but a single pole key switch is required for each playing key.

These and other objects and advantages of the invention will become apparent from the following disclosure.

The accompanying drawing is a schematic circuit diagram of a complete pedal tone generating system according to the invention.

Referring to the drawing, the reference characters 100 represent the 13 pedal keys of a pedal clavier. Associated with each pedal key is a single pole switch 102. Transistors 103 and 104 together with their associated components 105 through 114 comprise a two-stage common emitter voltage amplifier. This amplifier is made into an oscillator by feeding back ener gy from the output through the capacitor 115 and resistors 116 and 117 to the base of transistor 103, the frequency of oscillation is determined by the resonant circuit including inductor 118 and capacitor 119, which is connected to ground through the resistor 120, which also serves as the emitter resistor of transistor 122. In order to tune the oscillator to any one of the l3 semitones represented by the 13 pedal keys, 1 have provided means for varying the effective capacitance of capacitor 119. Since the charge that a capacitor is able to store is a function of its capacitance as well as of the voltage applied cross its terminals, it is possible to vary the effective capacitance by varying the instantaneous voltage. This is accomplished by applying an AC voltage to the lower terminal 124 of capacitor 119 which voltage is synchronous, but of a different amplitude than the voltage appearing on the upper terminal 126. The voltage to be applied to terminal 124 is developed across the emitter resistor 120 of the emitter follower circuit formed by transistor 122 in conjunction with resistors 120, 128 and 129. By adjusting the input to this emitter follower circuit, it is possible to adjust the amount of synchronous voltage applied to terminal 124 and therefore to adjust the effective capacitance of capacitor 119 and hence the frequency of the oscillator. Associated with the pedal keys 100, are a series of impedances 130. Signal frequency voltage appearing on terminal 126 of capacitor 119 is applied to the base of transistor 122 by means of resistors 132 and 133 and coupling capacitor 134. The junction of resistor 133 and capacitor 134 is connected to ground through the aforementioned string of impedances 130, and the exact voltage applied to the base of transistor 122 depends upon the relative impedances of resistors 132 and 133 as compared to the impedance from point 136 to ground. Associated with each of the i3 impedances is switching transistor 140.

Also associated with this transistor is the base return resistor 141, memory capacitor 142, and the memory discharge or shunting circuit including resistor 143 and diode 144. The entirety of this memory-switching circuit is enclosed within the dotted line 145. A similar circuit is provided for each of the series impedances 130, and these are indicated by the eleven dotted rectangles to the right of transistor 140. The battery represents a source of potential. lts negative terminal is grounded and its positive tenninal labeled plus 20 volts. The common terminal 152 of all of the key switches 102 is connected to the plus 20 volt potential through the emitterbase junction of transistor 153. When any key switch is closed, current will flow through this junction thus switching transistor 153 to a conducting mode and resulting in a voltage of approximately plus 20 volts being applied across collector resistor 156. Transistor 154 together with its load resistor 157 and 158 comprise an emitter follower, and accordingly whenever the plus 20 volts appear across the resistor 156 it will also appear across resistors 157 and 158. This voltage is used to operate the signal gating circuits which will be hereinafter described. Whenever transistor 154 is switched to the on condition, a base current will also flow in transistor 155, which results in the collector of transistor being brought to ground potential. Since the collector is connected to the bus bar 170, the result is that whenever any pedal key is depressed, the bus bar is effectively connected to ground potential and the memory capacitor shunting circuits consisting of diodes 144 and resistors 143 are effectively connected across the capacitors 142.

Thus far I have described the operation of the oscillator and the tuning circuits whereby the operation of a single switch tunes the oscillator to any one of the l3 pitches represented by the 13 pedal keys. Referring again to the drawing, 1 will now describe the operation of the audio and gating circuits. The output of the oscillator is connected to a bufier circuit including transistor and resistors 176 and 177. The output of the buffer is used to trigger a pair of cascaded frequency dividers 180 and 180a, which may be of the flip-flop type. The circuit for one suitable flip-flop is shown enclosed within the dotted rectangle 180. Since flip-flops are commonly known in the art, I will not describe in detail the operation of this circuit. lt should be understood however, that whenever the flip-flop 180 is triggered by an incoming signal, in this case provided by the buffer transistor 175 and connected by way of capacitor 178, an output signal will appear at the terminal 182 which is in the form of a square wave signal having a frequency equal to one-half the frequency of the trigger signal. The rectangle 180a represents another flip-flop which may be identical to that shown at 180 and which has an output terminal 1820, upon which appears a square wave signal of one-half the frequency of that appearing on terminal 182. F lip-flop 18011 is 'driven by the output of flip-flop 180, which signal is fed through capacitor 186. Associated with output terminal 182 is a gating circuit including diodes 188 and 189 and resistors 190, 191 and 192. Whenever a pedal key is depressed, a voltage of approximately plus 20 volts appears at the emitter terminal of transistor 154 and this potential applied through diode 159 and resistor 160, results in an audio frequency signal having a square wave form to appear at the output of the gating circuit on terminal 193. The tone buildup and decay characteristics are determined primarily by resistors 160 and and capacitor 161. With switch 194 in the open position, the tonal decay may correspond to that of a string bass, closing switch 194, connects resistor 183 across capacitor 161, resulting in a rapid tonal decay. Numeral 195 represents an amplifier and 196, a loud speaker. Square wave signals are therefore applied to the amplifier 195 whenever stop switch 197 is closed. Transistor 198, capacitor 199 and resistors 200, 201 and 202 comprise a distorter circuit which differentiates the square wave output of the gate and rectifies the differentiated wave form to produce a complex wave having both even and odd order harmonics. This pulse wave is applied to the terminal 205 through coupling capacitor 203 and isolating resistor 204. Switch 206 is stop switch to connect this pulse wave form into the outputs system. Similar gating circuitry is provided for flip-flop 1800 which operates in the same manner to produce gated square wave and pulse wave forms at a frequency 1 octave lower than those signals provided by the gating circuits just described. Similar components have been labeled with identical reference characters followed by an a to indicate that they relate to the suboctave circuitry.

Others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features involved.

lclaim:

1. A multifrequency tone generator for an electrical musical instrument comprising:

an oscillator;

tuning means for selectively tuning said oscillator to any of a plurality of predetermined frequencies;

said tuning means including a plurality of serially connected impedances; i J

a plurality of key switches;

a plurality of switching transistors respectively associated with said key switches and with said impedances, whereby the number of said impedances effective to tune said oscillator is determined by which of said key switches is activated;

a memory circuit associated with each switching transistor;

a gating circuit operatively associated with said oscillator;

an outputsystem; and

and means actuated by the operation of any key switch for causing said gating circuit to gate signal from said oscillator into said output system, and for simultaneously disabling said memory circuits.

2. A multifrequency tone generator for an electrical musical instrument comprising:

an oscillator;

an impedance network, the impedance of which determines the frequency of said oscillator;

a plurality of playing key operated key switches;

an output system;

a gating circuit for causing signals generated by said oscillator to appear in said output system;

a plurality of electronic switch means respectively as sociated with said plurality of key switches. and each having a terminal which, when energized, causes said electronic switch means to alter the impedance of said impedance network, and thereby tune said oscillator to a frequency of a musical scale;

a plurality of memory circuitsrespectively associated with said plurality of electronic switch means;

a plurality of memory disabling circuits respectively associated with said memory circuits;

a sensing circuit for sensing the depressing of any playing key; and

and means whereby said sensing circuit during periods of key depression simultaneously actuates said gating circuit and said plurality of memory disabling circuits,

3. A multiple frequency tone generator for an electrical musical instrument comprising:

an oscillator;

an impedance network the impedance of which determines the frequency of oscillation of said oscillator;

a plurality of key switches;

a source of DC potential;

a plurality of DC controlled frequency changing circuits res ectivel associated with said plurality of switches and eac rnclu mg a term nal which when energized causes a change is the impedance of said impedance network; a plurality of memory capacitors respectively associated with said frequency changing circuits; a plurality of shunting circuits respectively associated with said memory capacitors; an output system including a loudspeaker; a signal gating circuit operatively associated with said oscillator and said output system; and circuit means operatively associated with said source DC potential and with said key switches whereby the operation of any key switch, a. energizes its associated frequency changing circuit and charges its associated memory capacitor, b. renders said gating circuit operative to gate signal into said output system, and c. renders said shunting circuits operative to rapidly discharge the memory capacitors associated with nonoperated key switches. 

1. A multifrequency tone generator for an electrical musical instrument comprising: an oscillator; tuning means for selectively tuning said oscillator to any of a plurality of predetermined frequencies; said tuning means including a plurality of serially connected impedances; a plurality of key switches; a plurality of switching transistors respectively associated with said key switches and with said impedances, whereby the number of said impedances effective to tune said oscillator is determined by which of said key switches is activated; a memory circuit associated with each switching transistor; a gating circuit operatively associated with said oscillator; an output system; and and means actuated by the operation of any key switch for causing said gating circuit to gate signal from said oscillator into said output system, and for simultaneously disabling said memory circuits.
 2. A multifrequency tone generator for an electrical musical instrument comprising: an oscillator; an impedance network, the impedance of which determines the frequency of said oscillator; a plurality of playing key operated key switches; an output system; a gating circuit for causing signals generated by said oscillator to appear in said output system; a plurality of electronic switch means respectively associated with said plurality of key switches, and each having a terminal which, when energized, causes said electronic switch means to alter the impedance of said impedance network, and thereby tune said oscillator to a frequency of a musical scale; a plurality of memory circuits respectively associated with said plurality of electronic switch means; a plurality of memory disabling circuits respectively associated with said memory circuits; a sensing circuit for sensing the depressing of any playing key; and and means whereby said sensing circuit during periods of key depression simultaneously actuates said gating circuit and said plurality of memory disabling circuits.
 3. A multiple frequency tone generator for an electrical musical instrument comprising: an oscillator; an impedance network the impedance of which determines the frequency of oscillation of said oscillator; a plurality of key switches; a source of DC potential; a plurality of DC controlled frequency changing circuits respectively associated with said plurality of switches and each including a terminal which when energized causes a change is the impedance of said impedance network; a plurality of memory capacitors respectively associated with said frequency changing circuits; a plurality of shunting circuits respectively associated with said memory capacitors; an output system including a loudspeaker; a signal gating circuit operatively associated with said oscillator and said output system; and circuit means operatively associated with said source DC potential and with said key switches whereby the operation of any key switch, a. energizes its associated frequency changing circuit and charges its associated memory capacitor, b. renders said gating circuit operative to gate signal into said output system, and c. renders said shunting circuits operative to rapidly discharge the memory capacitors associated with nonoperated key switches. 